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How Many Coats of Polyurethane Do I Need? Solved!

polyurethane

polyurethane

Polyurethane is a protective, hardwearing finish that can be applied to wood and other surfaces. It is used to protect from scratches, abrasion, chips, and other blemishes. On external surfaces, it can protect against harmful chemicals present in bird droppings. On internal flooring, it can also provide a water-resistant finish. As well as offering a gleaming finish on wood and engineered wood surfaces, it provides a beneficial layer on the surface of concrete and even steel and non-ferrous metals, although its most common application is on wood floors inside the home.

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Can I Use Just One Coat of Polyurethane?

A single layer of polyurethane, or any oil-based finish, does not offer enough protection. The majority of this layer will be absorbed by the wood, which means that very little of the liquid will be left on the surface. Therefore, a second coat is required, because this will sit on and protect the surface of the material that is being coated. The type of material that you are treating, and how it is used, may mean that a third coat is necessary. The quality of the polyurethane agent is also important. Thinner treatments will require a third coating, so while these may be less expensive by the gallon, they can work out more expensive because you will need a lot more of the liquid application.

Whether you need two or three coats will depend on the surface and how you use it. You will also need to ensure that you apply the polyurethane coats properly, leave adequate time between applications, and maintain the polyurethane coating to get the longest-lasting results.

Are Two Coats of Polyurethane Enough?

You will need either two or three coats of polyurethane and you will have to wait until the second coat is applied to determine whether you need a third. However, there are some steps you can take that will help improve the performance of the protective coat.

  • Always start by sanding the wood. This not only gives a better-looking finish, but unsanded wood is more porous and will soak up more of the liquid that you apply. It is also more difficult to work with: you will struggle to get the brush into the holes and around the rough edges of the untreated wood.
  • Once you’ve sanded, you will need to remove the wood dust that is left over. If you fail to remove dust, it will be sealed under the polyurethane, and its frictionless adherence means that it can prevent the poly liquid from properly adhering to the wood surface. Brush off excess dust, use a vacuum, or even blow dust through an open window using a fan.
  • Oil-based polyurethane is easier to work with and more readily available in DIY and hardware stores. However, it takes longer to dry and will usually require more coats. Water-based options are more difficult to come by but they can take fewer coats to finish.
  • If you expect to use three coats, it means that you don’t have to apply each coat as thick as you would with a two-coat approach. A third coat may add time to the project, but could actually end up costing you less in the short and long run.

Are You Supposed to Sand Between Coats of Polyurethane?

It is commonplace to sand between coats of polyurethane. Some people argue that this is done to rough up the surface and, therefore, increase the adhesion of the liquid. However, it is far more important to ensure that sanding removes any dirt and dust that might have adhered to the last surface of polyurethane.

Can You Apply A Second Coat of Polyurethane Without Sanding?

If you are adding three coats of polyurethane, you might get away without sanding before the second coat, but this can leave debris and bits of dust under the finish. This will detract from the lacquered and smooth finish that polyurethane coating aims to provide. As such, we always suggest that you sand between each coat to ensure a better-looking finish.

Can You Put Too Many Coats of Polyurethane On?

Adding a fourth, fifth, or more coats of polyurethane will not really do any damage to the surface, but it won’t provide any benefit, either. By the time you’ve added a third coat, the entire surface has been covered and is protected from abrasion and other damage. Adding additional coats will not increase the level of protection, nor will it increase the buff or shine of the surface. Even if additional coats do offer a minimal increase in protection, this is far outweighed by the cost of the extra layers.

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Do You Really Need Three Coats of Polyurethane?

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Image Credit: John Loo, Flickr

It may not be necessary to add a third coat of polyurethane. If your wood floor is in good condition, you use a high-quality water-based polyurethane, apply it generously, and sand it well before each layer, you should find that two layers will suffice, especially if the floor is indoors and in a low-traffic area that will suffer minimal damage.

How Long Do I Have to Wait Between Coats of Polyurethane?

When it comes to waiting time, you either have to apply the next coat within two or three hours or wait for 24 hours or more. Follow the guidelines provided on your tin of coating. If you apply extra coats too soon, you will end up with ripples and bubbles between the layers. If you wait too long, the last layer may suffer some damage. If you wait longer than 24 to 48 hours, you will have to sand the last layer down before applying the next.

How Do You Remove Brush Marks from Polyurethane?

Brush marks can ruin a coated surface. Fortunately, though, you can fix the problem without having to try and remove the entire layer of polyurethane, and the process is quite simple. Use fine-grit sandpaper and sand the brush marks lightly. Remove dirt and debris by brushing the area down after. Reapply the finish, ensuring that you remove any excess from the brush, to minimize the chances of applying more brush marks.

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How Many Coats of Polyurethane Is Enough?

Polyurethane is an attractive and protective floor coating. It can be applied easily and, depending on the surface as well as the quality of the finish itself, it will usually take two or possibly three coats of the liquid to ensure an even and total covering. Ensure that the surface is properly prepared before you start, that you sand between coats, and that you finish the final layer with minimal brush strokes, to get the best results.


Featured Image: Mr.Thanathip Phatraiwat, Shutterstock

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